1. Field of the Invention
The present invention relates to radio-frequency identification (“RFID”) technology, and deals more particularly with techniques for leveraging RFID technology to detect and/or prevent theft and shoplifting.
2. Description of the Related Art
Theft and shoplifting are problems in many environments. For retail businesses, for example, billions of dollars are lost every year to shoplifting. Several techniques exist to combat theft in the retail environment. As one example, some retailers station an employee at the store exit to visually verify that the merchandise in the customer's possession matches an itemized receipt that was issued at the point of sale. Of course, this approach is expensive for the retailer, and is often intimidating and humiliating for honest customers. Other approaches, also not cost-effective, include stationing employees to guard the merchandise, chaining high-value items to display shelves or placing them in locked display cases, and electronic surveillance (“EAS”).
Many technologies have been employed for EAS. The basic principle behind most prior-art EAS systems includes using a transmitter to create an electromagnetic field across the store's exit area and a receiver than can detect variations in the field. Small tuned circuits or magnetic material inside security tags that pass through the exit modify the field enough for the receiver to detect the change and activate an alarm. The retailer attaches the tags to high-risk items, and the EAS notifies him or her when a tag passes through the exit field. The security tag must be removed or deactivated at the point of sale to prevent the alarm from sounding. See “Stop! Thief” by Warren Webb, EDN, Jun. 21, 2001, pp. 52, 54, 56, for a review of prior-art EAS systems.
Passive EAS systems in use today typically operate at 8.2 MHZ, 9.5 MHZ, and other frequencies. EAS tags for garments may be detached at the point of sale using a special tool. EAS tags on smaller items, also called disposable labels, are designed to remain on the item but must be deactivated (detuned) at the point of sale. This is done by passing the tagged item near a strong electromagnetic filed, which changes the tuning of the passive antenna in the tag by destroying a fusible link, thus modifying the return signal detected when the item passes near the receiver.
The tags used by these types of prior-art EAS systems are completely passive.
More recently, a new technology called Radio Frequency Identification (“RFID”) has been introduced for labeling and tracking items of merchandise from manufacturing through distribution and retail sale. RFID differs from passive EAS technologies in several important ways. An RFID tag includes both passive elements (an antenna) and active elements (a read-write data memory, control circuitry, and a radio frequency transponder). RFID tags are typically not self-powered, but may receive their power via capacitative coupling from an external radio frequency source. When brought into proximity with an RFID reader at a typical effective distance of about 1 centimeter to 5 meters (depending on the type of tag), the RFID tag receives sufficient power to enable clocking the semiconductor and analog portions comprising the transponder, control circuits, and data memory through enough clock cycles that the tag can return the data bits from its memory as a digitally-encoded RF signal. This is advantageous because the tag can be read (or written) from a distance without the necessity of line-of-sight, as had been required to read a bar code with a laser scanner.
RFID technology has generally been utilized for inventory control (e.g., in a warehouse, manufacturing, or distribution facility) and for item identification at the point of sale as an improvement over today's nearly ubiquitous laser-scanned bar codes. Several large retailers have indicated a desire to begin using RFID tagging on all their merchandise. RFID tags can be created using relatively inexpensive manufacturing techniques: the antenna portion can be printed on packaging material with conductive carbon ink, and the semiconductor portion—as small as 3 millimeters square—can be mounted to the antenna with glue. The cost of RFID tags is expected to decline to the point of being cost-effective even on small-value retail items. Thus, it can be assumed that in the near future, RFID tags on merchandise will become nearly ubiquitous.
The use of RFID to deter theft has been suggested in several contexts. Notably, early RFID literature suggested that RFID could be used for improved inventory control, thereby preventing employees from stealing items from the store's inventory. The literature also suggested that RFID could prevent theft in the distribution chain between the manufacturer and retailer, by actively monitoring inventory in trucks and shipping containers to ensure that merchandise was not diverted to unintended destinations. Commonly-assigned, co-pending U.S. patent application Ser. No. 09/790,104 (filed on Feb. 21, 2001), entitled “Method to Address Security and Privacy Issues of the Use of RFID Systems to Track Consumer Products” (which is hereby incorporated herein by reference), discussed techniques for secure electronic labeling by overwriting RFID tags at the point of sale and by placing control bits into the RFID data memory, in order to prevent an unscrupulous store employee from reprogramming the RFID tag of an expensive item with data representing an inexpensive item, in order to pay a lower price for the expensive item.
The read-write data memory in today's RFID tags is non-volatile and typically has a capacity of 5 to 256 bytes. The antenna in RFID tags can be printed on a product's packaging using conductive ink, as noted above. Or, rather than placing the tag on the packaging, it may be incorporated into the product (for example, by sewing an RFID tag into a garment, placing an RFID tag on a page within a book, and so forth). The memory typically stores an “Electronic Product Code” or “EPC”, a counterpart of the bar code, that assigns a searchable number to each object. The EPC identifies a consumer product individually, not just by type. Present versions of the code use 96 bits of information, which comprises an 8-bit header, two sets of 24 bits that identify the manufacturer and the product type (respectively), and a 40-bit serial number. Ninety-six bits encode enough information to uniquely identify trillions of objects. See “Beyond the Bar Code” and companion article “What's My Number” by Charlie Schmidt, Technology Review Magazine, March 2001, pp. 80–85.
Prior art techniques are deficient in several respects. Having an employee inspect each shopper's merchandise is not only expensive for the employer and embarrassing for the shoppers, as noted above, it is also prone to human error. Existing passive EAS technology leaves room for a number of improvements and adaptations. RFID tagging of merchandise is coming into use in retail environments, but as presently utilized this technology does not avoid the need to also tag the articles with traditional EAS tags for theft detection, or to disable the RFID tag at the point of sale as is generally done with passive disposable EAS tags. It is desirable to continue utilizing the RFID tag as a data transponder, without destroying the tag or deleting its data memory, after an item containing the tag has been purchased at a point of sale. It is also desirable to determine, on the spot, whether an item has been paid for, even if a transaction database in which transactions are recorded is unavailable. The present invention avoids deficiencies of the prior art, while providing effective techniques for shoplifting and theft detection.